This invention relates generally to steam turbines and more particularly to drain purge systems for steam turbines.
At least some known steam turbines include a casing comprising an upper half shell and a lower half shell formed together at a joint. The joined half shells make up a casing that surrounds the rotating member of the turbine. During operation, condensed water may collect in the lower half shell. The water is removed using drain orifices formed in the lower half of the shell. Moisture collected in the lower half shell is routed to the drain orifices. During extended periods of operation, the drain orifices can become clogged from dirt, scale or chemical deposits. Clogged orifices cause excessive moisture to remain in the steam path. Excessive moisture tends to increase erosion of components within the steam path.
In some known steam turbines, the deposits collected in the drain orifices are removed from the drain orifices by shutting down and disassembling the steam turbine. Therefore, the drain orifices are only accessible for cleaning during a major maintenance outage.